It is known that an cyclic carbonate may react with a compound having an alcoholic hydroxyl group to produce a linear carbonate adduct of these reactants. To our best knowledge, however, a curable resin system utilizing this reaction as the crosslinking mechanism thereof has not been known yet. Since the above reaction is an addition reaction producing no reaction by-product and since a chemically stable carbonate linkage is newly formed, the above curable resin system may find use in coating and other applications where excellent acid- or other chemical resistances are desired in the cured product thereof while minimizing volumetric shrinkage upon curing.
Recently, Endo et al. reported a system in which polymers having a plurality of pendant cyclic carbonate groups produced by copolymerizing a cyclic carbonate having a vinyl group with a conventional vinyl monomer are crosslinked with sodium methoxide or a diamine. Polymer Preprints, Japan, vol. 41, No. 2, 318 (1992); and ibid., vol. 42, No. 2, 244 (1993). This system, however, does not utilize the addition reaction between a cyclic carbonate group and an alcoholic hydroxyl group as the crosslinking mechanism thereof.
JP-A-04285623, JP-A-04325538 and JP-A-04325539 disclose curable resin compositions containing polymers having a plurality of 5-membered cyclic carbonate groups, namely 1,3-dioxolane-2-one-4-yl groups. These systems are distinguished from the present invention in that not only the cyclic carbonate group is a 5-membered ring but also the crosslinking mechanism does not solely relies on the addition reaction of a cyclic carbonate group with an alcoholic hydroxyl group.